During refueling of nuclear reactors a canal above the reactor vessel is filled with water submerging the interior of the reactor. To limit radioactive contamination it is imperative that none of the water above and within the vessel be allowed to penetrate the lower space around the exterior of the reactor vessel and within the reactor cavity. Since this annular space may not be permanently sealed it has been recognized that temporary reactor cavity pool seals must be provided during the refueling process. An improvement over earlier seals is disclosed in U.S. Pat. No. 4,214,760. The present invention is a specific advance over the structure disclosed in that patent.
The prior art structure referred to includes a removable annular seal plate which has an upper surface substantially coplanar with both a cavity wall ledge and an upper surface on a flange disposed about the reactor vessel. The seal plate also has a circular edge surface which is spaced in opposition to a circular face either beneath that ledge and/or beneath the reactor vessel flange upper surface. Annular inflatable means are provided to effect a seal between the spaced circular surface and the face.
What is referred to above as the cavity ledge is typically a metal ring embedded within the cylindrical concrete wall surrounding the reactor vessel. This concrete wall extends straight downwardly from the inner periphery of the embedment ring. The flange surrounding the reactor vessel is nominally, but not necessarily exactly, concentric with the embedment ring. If they are eccentric to any significant degree, say more than one or two inches off-center, then the structure disclosed in U.S. Pat. No. 4,214,760 will no longer be servicable, because the annular inflatable means will not make effective sealing engagement between the spaced circular surface and face.
Another disadvantage of the structure of the aforementioned prior art patent is that the inflatable means sealing directly against the embedment ring requires for proper operating clearance a circumferential notch in the concrete cavity wall immediately below the ring.
It is the principal purpose of the present invention to improve on the structure of the aforementioned patent so that it is no longer sensitive to the parameter of eccentricity. If due to settling of the building structure or for any other reason the embedment ring and reactor vessel flange become eccentric beyond otherwise acceptable limits, the structure of the present invention nonetheless allows the inflatable seal to operate between opposed sealing surfaces which are exactly concentric. Also no notching of the concrete cavity wall is required in the arrangement of the present invention.